Looking at the Batt Bridge circuit:
http://www.evdl.org/pages/battbridge.html
You can see that it connects to the pack at 3 points:
bottom, mid and top.
So, in order to cut the current, you need to disconnect at least 2.
This can easily be done adding a reed relay in series with the two resistors
so the pack+ flows through the resistor, then through the contact of the reed
relay,
then to the red and/or green LED. From the bottom of the green LED, you go
through
the contact of the second reed relay, then through the second resistor and to
pack-.
The two coils of the two reed relays can be connected to IGN (Ignition) and
ground.
Make sure they are 12V reed relay coils.

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Note that the resistors are suggested to be dimensioned for 20mA.
That was a good value for older, low efficiency / low brightness LEDs.
Today you can buy LEDs that you cannot look at directly, lest you risk eye
damage at 20mA.
So you may need to design for a lower current through the green LED.
One way to do this is to add a resistor in parallel to the green LED, so most
of the current
bypasses the LED and the LED will be less bright.
You can also increase the resistance of the two resistors R1 and R2 but this
makes the
circuit less sensitive to imbalance because there is less current change per
Volt of imbalance.
This sensitivity can be improved again by adding a zener in series with the
resistor, but now
we are starting to design a more complex product again...
Cor.
-----Original Message-----
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Kevin Trombley via EV
Sent: Saturday, January 06, 2018 7:08 AM
To: ev@lists.evdl.org
Cc: Kevin Trombley
Subject: [EVDL] Batt-Bridge questions
Thank you, for the detailed info.
I am not sure how to check LED's but,
to check if a Batt-Bridge is assembled & functioning properly you just connect
it to a battery pack & the green LED should be the only one lit.
Then, if the positive lead is disconnected the negative side red LED should
light up or if the negative lead is disconnected the positive side red LED
should light.
Like this El Moto part 33 Battery Pack Balance Monitor
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El Moto part 33 Battery Pack Balance Monitor
This is 48V Battery Pack Balance Monitor that I assembled based on Lee Hart's
Batt-bridge. | |
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Another question, if I may
Would it affect sensitivity or performance if a switch was added to be able to
turn it off when not in use or for long term storage?
I understand from personal testing that (2) leads would need to be switched.
Either (2) switches or a dpst switch.
If it's plausible to be switched, could a couple of relays be used, so it can
be switched on & off by the vehicle ignition?
Thanks again, Kevin
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